Email Validation using Python Regular Expression

Question

I have 9 email patterns. I expect:

and

Then, I have made script of regex like:

regex = r"(^[a-zA-Z_]+[\.]?[a-z0-9]+)@([\w.]+\.[\w.]+)$"

But, email [email protected] is still valid.

How to make the right pattern regex so that email become not valid, and all of email patterns can fit to my expectation?

Maybe ^(?![a-zA-Z]+\.\d+@)[a-zA-Z_]+(?:\.[a-z0-9]+)?@[\w.]+\.\w+$ will do, see demo. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Apr 9, 2020 at 14:22
Perhaps with an optional part matching the underscore or start the match with a-z before the dot ^[a-zA-Z]+(?:(?:(?:_[a-zA-Z0-9]+)+\.[A-Za-z0-9]+)|\.[a-zA-Z][a-zA-Z0-9]*)?@\w+(?:\.\w+)+ regex101.com/r/Q3TxQc/1 — The fourth bird
– The fourth bird, Commented Apr 9, 2020 at 17:00

The fourth bird · Accepted Answer · 2020-04-09 21:53:27Z

1

For the example data you could either match an optional part with underscores where a dot followed by a digit is allowed before the @

Or you match a part that with a dot and a char a-z before the @

 ^[a-zA-Z]+(?:(?:_[a-zA-Z0-9]+)+\.[A-Za-z0-9]+|\.[a-zA-Z][a-zA-Z0-9]*)?@(?:[a-zA-Z0-9]+\.)*[a-zA-Z0-9]{2,}$

Explanation

^ Start of string
[a-zA-Z]+ Match 1+ times a char a-z
(?: Non capture group
- (?:_[a-zA-Z0-9]+)+ Repeat 1+ times an underscore followed by a char a-z or digit 0-9
- \.[A-Za-z0-9]+ Match a dot and 1+ chars a-z or digit 0-9
- | Or
- \.[a-zA-Z][a-zA-Z0-9]* Match a a dot and a single char a-z and 0+ chars a-z or digits
)? Close group and make it optional
@ Match literally
(?:[a-zA-Z0-9]+\.)* Repeat 0+ times a-z0-9 followed by a dot
[a-zA-Z0-9]{2,} Match a-z0-9 2 or more times
$ End of string

answered Apr 9, 2020 at 18:26

The fourth bird

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Comments

Ωmega · Accepted Answer · 2020-04-09 20:21:58Z

0

Use the following regex pattern with gmi flags:

^[a-z]+(?:(?:\.[a-z]+)+\d*|(?:_[a-z]+)+(?:\.\d+)?)?@(?!.*\.\.)[^\W_][a-z\d.]+[a-z\d]{2}$

answered Apr 9, 2020 at 20:13

Ωmega

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